BACKGROUND: Magnetic resonance imaging (MRI) is used to measure the diameter and volume of the left atrium in patients with nonobstructive hypertrophic cardiomyopathy (NOHCM). However, these morphological data cannot explain the complexity of left atrial (LA) function. The study aimed to evaluate LA function by applying cardiac magnetic resonance feature tracking (CMR-FT) for LA strain analysis in patients with NOHCM, and to examine the impact of NOHCM on LA and left ventricular (LV) structure and function. METHODS: We collected retrospectively clinical and MRI data from 58 patients with NOHCM (NOHCM group) and 30 healthy controls (HC group) and measured the LA volume index (LAVI) and overall LA functional parameters, which included myocardial reservoir parameters [total strain (εs), peak positive strain rate (SRs), and LA total ejection fraction (LATEF)], conduit parameters [passive strain (εe), peak early negative strain rate (SRe), and LA passive ejection fraction (LAPEF)], and booster pump parameters [active strain (εa), peak late negative strain rate (SRa), and LA active ejection fraction (LAAEF)]. Additionally, LV functional parameters [LV ejection fraction (LVEF), LV cardiac output (LVCO), and LV cardiac index (LVCI)] and structural parameters [LV maximal wall thickness (LVWT RESULTS: The NOHCM group had significantly higher values of LVWT CONCLUSIONS: The measurement of LA strain by CMR-FT is a feasible and reliable method for assessing LA function. Myocardial reservoir and conduit function of the LA decline prior to LA enlargement, and strain parameters enable early detection of LA dysfunction. The combination of LA strain parameters with ejection fraction provides added value in diagnosing LA dysfunction. LA ejection fraction (LAEF) across all phases of the LA cycle shows a strong correlation with strain parameters.